Washington: The personal security of Dr Anthony Fauci, the top US expert on infectious diseases, has been enhanced after he received threats following his pleas to Americans to follow strict social distancing rules to help slow the spread of the coronavirus pandemic, according to media reports.

The 79-year-old doctor, a key member of President Donald Trump's coronavirus task force, has been the most outspoken advocate of social distancing rules that have shuttered the country's schools, forced businesses to close, kept people in their homes and battered the US economy.

"That has made him a target of online conspiracy theorists who have accused Dr. Fauci, a long-time scientist and civil servant who has served presidents of both parties, of trying to undermine Mr. Trump during a year in which the president is fighting for re-election," The New York Times reported.

The idea that the top infectious-diseases expert is responsible for the country's hardship — and for whatever political damage President Trump might suffer as a result — was fuelled in part by a moment during a news briefing in which Fauci dropped his head and touched his forehead as the president was speaking.

The image went viral online and Right-wing supporters of Trump cited it as evidence that Fauci sought to undercut the president, the newspaper reported.

The Department of Health and Human Services granted the enhanced personal security for Fauci, after the Justice Department signed off on a request for extra agents to guard him, the report quoted officials as saying.

The concerns include threats as well as unwelcome communications from fervent admirers, The Washington Post quoted people with knowledge of deliberations inside the Department of Health and Human Services and the Department of Justice as saying.

Fauci has become a public target for some right-wing commentators and bloggers, who exercise influence over parts of the president's base. As they press for the president to ease restrictions to reinvigorate economic activity, some of these figures have assailed Fauci and questioned his expertise, the newspaper noted.

A law enforcement official told CNN that the Department of Health and Human Services Inspector General, the agency's law enforcement arm, asked the US Marshals Service for assistance following threats to Fauci. The Marshals then deputed HHS officers to act as personal security for the doctor.

The report quoted a source as saying that the stepped up visible police presence was a response to growing threats to Fauci's safety, though the source of the threats was not identified.

The coronavirus could kill 100,000 to more than 200,000 Americans in the coming weeks, Fauci has warned. He, along with a fellow task force member, Dr. Deborah Birx, have forced Trump to extend the amount of time that the country would remain shuttered through the end of this month.

Earlier, Trump said he wanted to end the social distancing guidelines in the country by Easter (April 12).

But Fauci was among the health advisers on Trump's team encouraging a continuation of the current guidelines after the President heard from business leaders and some of his conservative allies that the restrictions were more damaging than the virus itself.

During the White House coronavirus task force briefing with reporters on Wednesday, Fauci was asked whether he or White House coronavirus response coordinator Birx had received threats of any kind or whether they had been assigned a security detail. He said he was not able to answer.

"Anything that has to do with security detail I would have to have you (ask your question) to the inspector general of HHS," he said, referencing the Department of Health and Human Services.

Fauci's response was quickly interrupted by the president, who stepped up to the podium to say America's most visible infectious disease expert doesn't require protection.

"(He) doesn't need security, everybody loves them," said Trump. "Besides that, they'd be in big trouble if they ever attacked," the president added.

According to the Johns Hopkins Coronavirus Resource Centre, over 200,000 people in the US have been hit by the virus and some 5,100 others have died as on Thursday morning.